1. Field of the Invention
Linear motion, continuously variable, applied to a carrier provides transporting means with a capability of smooth acceleration and deceleration. Multiple carriers with a common power input provide transporting means without danger of collision between adjacent carriers. Such multiple carriers also provide means for stretching or compressing continuous lengths of material carried. A specific embodiment of such carriers finds use in the field of film stretching.
2. Discussion of the Prior Art
Mechanical devices useful for continuously stretching materials have long been sought, especially in the area of film web stretching and to the end of simultaneously stretching film webs in substantially perpendicular directions.
Japanese Laid-Open Publication No. 52-22669, published June 18, 1977, discloses a mechanical apparatus for stretching film by means of clips on rails whereby the clips are accelerated on the rails through a gear reduction with cog wheels of varying sizes in adjacent rack members.
U.S. Pat. No. 2,571,355, issued Oct. 16, 1951, discloses a device for two-way stretching of film wherein clips gripping the film are set to traverse grooves spiraled in corresponding faces of cones which have been situated apex-to-apex.
U.S. Pat. No. 3,248,753, issued May 3, 1966, discloses an alternative means for stretching film simultaneously and in perpendicular directions, utilizing directly-driven sprocket wheels of appropriate sizes with appropriate numbers of teeth.